"Some species of cuckoo are known as brood parasites for their devious tactic of laying their eggs in other species’ nests so those birds can care for the cuckoos’ young. Now scientists have discovered that an Australian bird called the fairywren has evolved a way around this tactic: The mothers teach their unborn chicks a unique begging call — a sort of password."
- Mark H
from Bookmarklet

"The teaching begins a few days before the birds hatch. And while “the cuckoo chick is very adaptable and tries out many begging calls until it sounds similar to the fairywren,” Dr. Hauber said, it also has a shorter incubation period. So it hatches several days before fairywren chicks, leaving it little time to practice and perfect the passwordlike call of the fairywren mother. "
- Mark H